Three different topics have been studied under this project: (a) we have completed an extensive four-year study of the general properties of cooperative steady-state enzymatic systems. Three-state Ising systems were studied further, as well as half-of-the-sites reactivity in a dimer; (b) double-stranded DNA can be unwound by ATP-dependent helicases and by treadmilling binding proteins, using the net free energy of DNA synthesis on the leading strand. These processes have been analyzed from a bioenergetic point of view, and a possible helicase model has been proposed; (c) we are continuing our work on explicit kinetic models of muscle contraction.